/*========================== begin_copyright_notice ============================

Copyright (C) 2017-2021 Intel Corporation

SPDX-License-Identifier: MIT

============================= end_copyright_notice ===========================*/

#include "Compiler/Optimizer/OpenCLPasses/BIFTransforms/BIFTransforms.hpp"
#include "Compiler/IGCPassSupport.h"

#include "common/igc_regkeys.hpp"

#include "common/LLVMWarningsPush.hpp"
#include "llvm/IR/Module.h"
#include "llvm/IR/Function.h"
#include "llvm/ADT/StringRef.h"
#include "common/LLVMWarningsPop.hpp"

using namespace llvm;

namespace {

class BIFTransforms : public ModulePass {
public:
  static char ID;
  virtual void getAnalysisUsage(llvm::AnalysisUsage &AU) const { AU.setPreservesCFG(); }

  BIFTransforms();

  ~BIFTransforms() {}

  virtual bool runOnModule(Module &M);

  virtual llvm::StringRef getPassName() const { return "BIFTransforms"; }

private:
  // Replace some BI Functions with faster versions, such as
  // length --> fast_length, etc.
  bool replaceBIF(Function &F);
};

} // namespace

// Register pass to igc-opt
#define PASS_FLAG "igc-bif-transforms"
#define PASS_DESCRIPTION "Perform BIF-related transformations, such as replacing length with fast_length, etc"
#define PASS_CFG_ONLY false
#define PASS_ANALYSIS false
IGC_INITIALIZE_PASS_BEGIN(BIFTransforms, PASS_FLAG, PASS_DESCRIPTION, PASS_CFG_ONLY, PASS_ANALYSIS)
IGC_INITIALIZE_PASS_END(BIFTransforms, PASS_FLAG, PASS_DESCRIPTION, PASS_CFG_ONLY, PASS_ANALYSIS)

char BIFTransforms::ID = 0;

BIFTransforms::BIFTransforms() : ModulePass(ID) { initializeBIFTransformsPass(*PassRegistry::getPassRegistry()); }

bool BIFTransforms::replaceBIF(Function &F) {
  // replace
  //    length --> fast_length
  //    normalize --> fast_normaliez
  //    distance --> fast_distance
  // As the fast version only exists for float/double in BIF, not half,
  // here make sure F is not half before replacing.
  Function::arg_iterator AI = F.arg_begin();
  if (AI == F.arg_end()) {
    return false;
  }
  Type *Ty = AI->getType();
  if (Ty->isHalfTy() || (Ty->isVectorTy() && Ty->getContainedType(0)->isHalfTy())) {
    return false;
  }

  bool changed = false;
  StringRef name = F.getName();
  if (name.startswith("_Z6length")) { // length --> fast_length
    std::string newName("_Z11fast_length");
    newName.append(name.data() + 9);
    F.setName(newName);
    changed = true;
  } else if (name.startswith("_Z9normalize")) { // normalize --> fast_normalize
    std::string newName("_Z14fast_normalize");
    newName.append(name.data() + 12);
    F.setName(newName);
    changed = true;
  } else if (name.startswith("_Z8distance")) { // distance --> fast_distance
    std::string newName("_Z13fast_distance");
    newName.append(name.data() + 11);
    F.setName(newName);
    changed = true;
  }

  return changed;
}

bool BIFTransforms::runOnModule(Module &M) {
  // OCL builtin uses SPIR name mangling (Itanium C++ ABI + extension)
  //  mangledName (n) = _Z<lengthof(n)><n><type>
  bool changed = false;
  for (Function &F : M) {
    if (F.isDeclaration()) {
      if (IGC_IS_FLAG_ENABLED(EnableIntelFast) && replaceBIF(F)) {
        changed = true;
      }
    }
  }
  return changed;
}

// Public interface to this pass
ModulePass *createBIFTransformsPass() { return new BIFTransforms(); }
